In modern switched telecommunications systems (in particular, modern Public Switched Telephone Networks (PSTNs) and Public Land Mobile Networks (PLMNs)) it has become common practice to provide two related but separate network infrastructures: a bearer or transmission network for carrying end-user voice and data traffic, and a signalling network for controlling the setup and release of bearer channels through the bearer network in accordance with control signals transferred through the signalling network (sometimes known as out-of-band signalling). In practice, such signalling networks comprise high-speed computers interconnected by signalling links; computer programs control the computers to provide a set of operational and signalling functions in accordance with a standardised protocol.
One example of such a signalling protocol is the Signalling System No. 7 (SS7), whether as specified by the CCITT, ANSI, ETSI (for GSM), Bellcore or similar body, such a network being herein referred to as an SS7 network. As is known in connection with such networks, signalling information is passed over the signalling links to carry out particular a signalling conversation, or transaction.
Since there may be a number of different protocols carried on the network being monitored, the particular protocol of a transaction must be determined before the messages relating to that transaction can be decoded and analysed. This may be achieved by manual reconfiguration through static data defining the protocol running on each link, when it is known. However, where multiple links are involved (for example where a number of links are multiplexed together), this procedure is tedious and error-prone. Furthermore, any changes to the network require an additional manual step to reconfigure the monitoring system. Any delay between changes in the network and reconfiguration causes data loss, and may cause unexpected results.